The present invention relates generally to antenna-based communications and more particularly to antenna-array based communication systems.
Signal-sensing arrays find applications in many areas, including noise suppression, signal enhancement, and selective signal extraction. Most sensing arrays are placed on a platform, or equivalent structure, and are separated by a known and predictable distance. The signal of interest has a first source of origin, which is physically different than that of interference signals and noise signals. By taking note of the shift in time from when the signals hit the first array sensor to the time when the signals hit the last array sensor it is possible to selectively amplify or attenuate signal components having different physical origins. Not uncommonly in the realm of radio frequencies, platforms are equipped with an array of antennas that are separated by a xc2xc wavelength, or other predefined distance that is particularly suited for the anticipated application. Such systems are effective not simply as a means for isolating signals that are received; they also find application as a means for promoting effective directional signal transmission, achieving increased data-target specificity, and utilizing less power for data delivery.
In many situations the platforms upon which antennas are positioned are unwieldy and difficult to move. Further, in hostile environments, such as mountain ranges, glaciers, or areas where conventional vehicular access is difficult or impossible, platform based antenna arrays are not practicable. Naturally it is often in these environments where antenna arrays would be most useful. The battlefield environment is another area where antenna arrays find application. Terrestrial impediments result in signal scattering, multi-path fading problems, and intentional and unintentional jamming by other signals. Additionally, in hostile settings such as the battlefield, an antenna array may present an easy target for destruction by an adversary. Finally, in all applications, existing arrays are difficult to transport and use in remote environments. Thus, to be fully effective, an array will often need to be transported in disassembled form and reassembled at the destination before being used. This can cause hardship to prospective users, who may effectively be denied communication services for a time and exposed to the environment during the assembly process.
Therefore there is a need for an antenna array that can be easily transported, is functionally robust, difficult to destroy, and is suitable for use in a dynamic environment.
The present invention provides an antenna array that can be easily transported, is functionally robust, difficult to destroy, and is suitable for use in a dynamic environment.
The present invention allows an ad-hoc assembly of the array elements to form a functional antenna array. The ad-hoc structure allows each antenna to be in a different, non-immediate, location and yet allows the antennas to cooperate, and form a functional array.
One embodiment of the present invention includes a plurality of local nodes, which are configured to receive and transmit electromagnetic radiation on at least one channel. A blind source separation element is operatively interconnected to the plurality of local nodes. This blind source separation element may be physically located, at a central location, within one of the nodes, or distributed among a plurality of nodes. In the latter case, a central processor could utilize a plurality of nodes"" computational resources. Further there is a host node, which is a distance from the plurality of nodes. The host node is communicatively linked with the plurality of local nodes and is configured to receive and transmit electromagnetic radiation on at least one channel. The transmitted electromagnetic radiation initially, and at periodic intervals thereafter, will include a reference signal. The host node is configured to send a reference signal to the plurality of local nodes and the local nodes are configured to utilize the reference signal as a means for configuring the blind source separation unit so that the nodes can separate incoming signals and selectively isolate the incoming signals from the host node. Finally the plurality of nodes can directionally transmit data signals to, and receive data signals from the host node utilizing blind beamforming techniques.
In another embodiment of the present invention, the first plurality of local nodes are in an organized static array. In this situation the nodes would be positioned once and allowed to remain statically in position. Alternatively the nodes could be in an organized dynamic array, a random static array, and a random dynamic array, or transition from one configuration to another in real time.
In another embodiment of the invention the host node is locally interfaced with a second plurality of nodes, and one of the first plurality of local nodes serves as a host node to the second plurality nodes. Thus host node also belongs to an antenna array.
In another embodiment of the present invention the reference signal is utilized to optimize the performance of the blind source separation element and a plurality of beamforming coefficients are developed by the first plurality of local nodes using the reference signal, and the plurality of beamforming coefficients are utilized by the first plurality of local nodes to form a virtual antenna array, whereby the first plurality local nodes directionally receive or transmit electromagnetic radiation.
In another embodiment of the present invention the reference signal is optimized, such that the Blind Source Separation processor can achieve algorithm convergence quickly and the first plurality of local nodes can adapt to changing reception patterns and relative motion effects quickly.
In yet another embodiment of the present invention the electromagnetic radiation containing a data signal is transmitted and received until the quality of the data signal drops below a predefined threshold, at which time a new reference signal is transmitted. This embodiment would find particular application in situations where the nodes are in motion either relative to one another, or movement of the host node. Naturally, relative motion, with respect to the host node would not preclude the host node from moving, or both the host node and the first plurality of local nodes, or just the first plurality of local nodes.